Resource management is a key component of mission critical Push-to-Talk (PTT) systems. There is an expectation that PTT systems can manage wireless resources and grant calls if the required resources are available and queue calls if the required resources are not. Further, there is an expectation that PTT communication should be available via broadband systems, such as a 3GPP (Third Generation Partnership Project) LTE (Long Term Evolution) communication system. In this environment, a call controller is no longer tightly coupled to a radio access network (RAN), making resource management more difficult. This is especially true when individual unicast bearers need to be established for each broadband subscriber.
Some broadband cellular radio systems, such as systems that operate pursuant to the 3GPP LTE and WiMAX (Institute of Electrical and Electronics Engineers (IEEE) 802.16) standards, use a Quality of Service (QoS) resource management approach in which a request for establishment of a Guaranteed Bitrate (GBR) bearer in a cell is either admitted or denied. However, the standards do not provide a capability for maintaining a queue of pending requests for radio frequency (RF) channel resources, instead providing that blocked calls are cleared from the system. This “Blocked Calls Cleared” (Erlang-B) approach is generally adequate for handling telephone calls. A call establishment request which occurs when no resources are available is provided a “fast busy signal,” which is also known as a “reorder” indication. By contrast, a PTT voice call establishment request in a trunked radio system, when no resources are available, has traditionally been placed in a queue of pending requests. This is referred to as a “Blocked Calls Queued” (Erlang-C) approach. Further, 3GPP LTE manages resource congestion by using an Allocation and Retention Priority (ARP) preemption mechanism, which allows a higher priority call to preempt an existing lower priority call. However, such preemption may be more objectionable to end users than would incurring extra delay while the call is being established.
It is difficult to add queuing functionality for blocked calls to a standard 3GPP LTE cellular system for several reasons. The 3GPP LTE cellular standards do not define a method which would allow an eNodeB base station to indicate when channel capacity has become available in one of its RF cells that could be used to establish a new GBR bearer. Further, there is the additional challenge that independent LTE Application Function (AF) network elements, using separate LTE Policy and Charging Rule Functions (PCRFs), could compete for resources in a single congested LTE cell. There is no standardized LTE protocol which would allow independent AFs to coordinate their resource requests so that a single common queue of pending requests for resources in a congested cell could be maintained.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention. It will further be appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. Those skilled in the art will further recognize that references to specific implementation embodiments such as “circuitry” may equally be accomplished via replacement with software instruction executions either on general purpose computing apparatus (e.g., CPU) or specialized processing apparatus (e.g., DSP). It will also be understood that the terms and expressions used herein have the ordinary technical meaning as is accorded to such terms and expressions by persons skilled in the technical field as set forth above except where different specific meanings have otherwise been set forth herein.